Microchip Technology MCP1631RD-MCC2 データシート
2006-2012 Microchip Technology Inc.
DS41291G-page 61
PIC16F882/883/884/886/887
3.7
PORTE and TRISE Registers
PORTE
(1)
is a 4-bit wide, bidirectional port. The
corresponding data direction register is TRISE. Setting a
TRISE bit (= 1) will make the corresponding PORTE pin
an input (i.e., put the corresponding output driver in a
High-Impedance mode). Clearing a TRISE bit (= 0) will
make the corresponding PORTE pin an output (i.e.,
enable the output driver and put the contents of the
output latch on the selected pin). The exception is RE3,
which is input only and its TRIS bit will always read as
‘1’.
TRISE bit (= 1) will make the corresponding PORTE pin
an input (i.e., put the corresponding output driver in a
High-Impedance mode). Clearing a TRISE bit (= 0) will
make the corresponding PORTE pin an output (i.e.,
enable the output driver and put the contents of the
output latch on the selected pin). The exception is RE3,
which is input only and its TRIS bit will always read as
‘1’.
shows how to initialize PORTE.
Reading the PORTE register (
) reads the
status of the pins, whereas writing to it will write to the
PORT latch. All write operations are read-modify-write
operations. Therefore, a write to a port implies that the
port pins are read, this value is modified and then
written to the PORT data latch. RE3 reads ‘0’ when
MCLRE = 1.
PORT latch. All write operations are read-modify-write
operations. Therefore, a write to a port implies that the
port pins are read, this value is modified and then
written to the PORT data latch. RE3 reads ‘0’ when
MCLRE = 1.
The TRISE register (
) controls the PORTE
pin output drivers, even when they are being used as
analog inputs. The user should ensure the bits in the
TRISE register are maintained set when using them as
analog inputs. I/O pins configured as analog input always
read ‘0’.
analog inputs. The user should ensure the bits in the
TRISE register are maintained set when using them as
analog inputs. I/O pins configured as analog input always
read ‘0’.
EXAMPLE 3-6:
INITIALIZING PORTE
Note 1: RE<2:0> pins are available on
PIC16F884/887 only.
Note:
The ANSEL register must be initialized to
configure an analog channel as a digital
input. Pins configured as analog inputs
will read ‘0’.
configure an analog channel as a digital
input. Pins configured as analog inputs
will read ‘0’.
BANKSEL PORTE
;
CLRF
PORTE
;Init PORTE
BANKSEL ANSEL
;
CLRF
ANSEL
;digital I/O
BCF
STATUS,RP1
;Bank 1
BANKSEL TRISE
;
MOVLW
B‘00001100’ ;Set RE<3:2> as inputs
MOVWF
TRISE
;and set RE<1:0>
;as outputs
;as outputs
REGISTER 3-13:
PORTE: PORTE REGISTER
U-0
U-0
U-0
U-0
R-x
R/W-x
R/W-x
R/W-x
—
—
—
—
RE3
RE2
RE1
RE0
bit 7
bit 0
Legend:
R = Readable bit
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
bit 7-4
Unimplemented: Read as ‘0’
bit 3-0
RD<3:0>: PORTE General Purpose I/O Pin bit
1 = Port pin is > V
1 = Port pin is > V
IH
0 = Port pin is < V
IL
REGISTER 3-14:
TRISE: PORTE TRI-STATE REGISTER
U-0
U-0
U-0
U-0
R-1
(1)
R/W-1
R/W-1
R/W-1
—
—
—
—
TRISE3
TRISE2
TRISE1
TRISE0
bit 7
bit 0
Legend:
R = Readable bit
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
bit 7-4
Unimplemented: Read as ‘0’
bit 3-0
TRISE<3:0>: PORTE Tri-State Control bit
1 = PORTE pin configured as an input (tri-stated)
0 = PORTE pin configured as an output
1 = PORTE pin configured as an input (tri-stated)
0 = PORTE pin configured as an output
Note 1:
TRISE<3> always reads ‘1’.